class_docstr: An encapsulation of a change to be made to the tree.
  Constructed of three components
    - the node to be changed
    - what it should be changed to
    - a string name of the kind of change (normally grow or prune)
code: def __init__(
      self, kind: str, existing_node: TreeNode, updated_node: TreeNode
  ):
      self.kind = kind
      self.existing_node = existing_node
      self.updated_node = updated_node
  
file_path: imodels/imodels/experimental/bartpy/mutation.py
imports: from .node import TreeNode, DecisionNode, LeafNode
label_desc: Use image node_id 1 to create a new TreeMutation object from inherited base classes: object with example: obj = TreeMutation(kind, existing_node, updated_node)